This is an application for continuation of an existing study of the early, mid, and late-life factors contributing to the onset and course of Alzheimer's disease (AD). This research uses archival longitudinal data from a volunteer sample of N=678 Catholic Nuns, aged 75 to 103 (in 1991). The investigators seek to continue the evaluation of this cohort for risk factors for Alzheimer's disease (AD) until the year 2001. The proposal seeks to substantiate preliminary findings that AD is not an inevitable consequence of biologic aging and that AD is related to early life factors, and analyzes the effects of genetic markers and other, later risk factors for AD.